By DAVID DeWITT

August 20, 2014

Quietly observant, “Precious Caterpillar” is a grass-roots documentary — or a dirt documentary, given that it’s devoted to watching Tibetans dig for caterpillar fungus.

That’s the movie.

The fungus — it escapes from the caterpillar it has killed each spring — is coveted for its medicinal properties: strengthening the immune system, neutralizing the nastier side effects of chemotherapy, and the like. Many low-income Tibetans make annual journeys of hundreds of miles to the high-altitude hills where the fungus crop is good; a pound of the treasure, one says, is worth three times his work for the rest of the year.

“Precious Caterpillar,” part of the ContemporAsian film series at the Museum of Modern Art, focuses mostly on Tsondru, a former monk who farms for his livelihood and each year becomes a migrant fungus gatherer. Without commentary, we watch as he, his family and his friends work together, pitching tents, shoveling snow and putting their fingers in the muddy soil, breaking apart the most stubborn sod while taking care to sustain the caterpillar’s environment.

There’s an implication that these rural Tibetans are precious themselves, and the cinematography — prosaic, searching and lovely at once — promotes the case, making accessible a world that otherwise seems out of reach. This is one of those documentaries that leave you wondering how cameras could have been present; the work, the trek, the conversation all seem to exist for us without mediation.

Well meaning though it is, “Precious Caterpillar” is sometimes hard to follow, and only the rare audience member will find it absorbing. But it has a Zen appeal. Sometimes the smallest action — seen just as it is, without elaboration — reveals a broader interdependent reality. Even a system that hinges on the finger-size remains of a grubby insect.

Precious Caterpillar

Opens on Thursday

Written, produced and directed by Dorjetsering Chenaktsang; directors of photography, Taklha Gyal and Mr. Chenaktsang; edited by Benjamin Sroussi; music by Charles Teissier. In Tibetan, with English subtitles. Running time: 1 hour 41 minutes. This film is not rated.